Deflection system



Jan.

S. l. TOURSHU ETAL DEFLECTION SYSTEM Filed June 22, 1950 INVENTORS SIb/:snm I TJUHSHDU Rn EWULCUII Janl, 1952 s. l. TouRsHou ETAL 2,580,977

DEFLECTION SYSTEM Filed June 22, 195o 2 SHEETS-SHEET 2 g4 7' i K f 77 L I (0); 1 g//f I INVENTCRS SIMECIN I .TDUHSHDU Patented Jan. 1, 1952 DEFLECTION SYSTEM Simeon I. Tourshou, Philadelphia, Pa., and Robert G. Wolcott, Haddon Heights, N. J., assignors to Radio Corporation of America, a corporation Y of Delaware Application June 22, 1950, Serial No. 169,655

9 Claims. (Cl. 315-217) The present invention relates to electrical damping systems of the reaction scanning power recovery type and more particularly to electromagnetic cathode ray beam deflection circuits of the type employed in television systems wherein a portion of the damped reactive energy in the deflection system is fedback for utilization by the deilection circuit to thereby improve the overall operating eiciency of the system.

The vpresent, invention furthermore relates to improvements in television cathode ray beam deilection circuits ofv the zoom variety. That is, deection circuits in which the degree of deflection may be instantaneously changed to alter the effective magnification of the scene appearing in the television picture viewing area.

In this regard the present invention is an improvement over the deflection system shown and described in another U. S. patent application, Ser. No. 90,612 entitled Television Deflection Power Recovery Circuit by Simeon I. Tourshou, led April 30, 1949, now Patent No. 2,555,831, granted June 5, 1951.V

. In this copending application there is shown and described a particularly simple and novel electromagnetic deflection system of the direct drive variety. That isa system in which the deflection yoke is connected in series with the anode circuit of the output tube. The present invention modifies this direct drive system to provide zoom control of the deflection amplitude. The good performance .of the arrangement provided by the present invention is greatly supported by the high efficiency of the basic deflection system forming the subject of the above identified case.

Before considering the novel aspects of the present invention it is well first to consider some of the points brought out by the above noted Patent No. 2,555,831.` For instance, in electrical circuits requiring damping action of some kind, it is proverbial that the overallefciency of operation is considerably lowered because of theenergy dissipated in the damping circuits, this energy not being gainfully utilized. In early television practice, cathode ray electromagnetic beam deflection systems suifered substantial losses in this respect, which in turn stimulated the development of power recovery deflection systems in which some of the stored electromagnetic reactive energy, normally dissipated in the damping system, is capaci tively stored and employed to eiect a boost in the B supply voltage applied to the vacuum tube driving the deflection system. Such power recovery or power feedback systems have greatly iinproved the operating efficiencies obtainable in deiiection systems as a whole. However, most prior art systems of this kind require the utilization of a deflection coupling transformer in order to realize reactive damping currents of proper magnitude to readily permit power feedback into the B supply circuit of the driving vacuum tube. The use of a transformer in this connection, of course, represents certain additional costs in circuit construction as well as introducing inherent losses in the system due to leakage reactance and magnetic hysteresis. The losses incurred through use of a transformer for coupling energy from the plate circuit of the deflection driving tube to the damped deflection yoke, of course, maybe obviated by direct inclusion of the yoke in the anode circuit of the vacuum tube. However, a direct drive reaction scanning connection of this type has not been regarded as readily lending itself to a high efficiency power recovery operation. Another problem in connection with such a direct drive system is that of obtaining sufficient linearity of sweep during thatA portion of the deiiection cycle supplied by the reaction scanning action.

Furthermore, in television receiver applications, the direct drive arrangement for the deflection yoke has inthe past displayed another awkward feature, that being the diiculty of obtaining from the deflection system an economical form of pulse step-up power supply for development of an accelerating potential for the associated cathode ray reproducing device.

In a copending application by Simeon I. Tourshou and kWilliam E. Scull, Jr., Serial No. 56,562, filed October 26, 1948 entitled High Voltage Power Supply, now Patent No. 2,555,827, granted June 5, 1951, this latter diiculty has been overcome in part through the use of an' auto trans'- former having its primary connected in series with the deflection yoke circuit. The high voltage pulses appearing in the secondary winding are then rectified to produce the appropriate high unidirectional beam accelerating potential. The inclusion of this autotransformer primary in the yoke circuit does, however, reduce to aconsiderable extent the operating voltage actually supplied to the anode of the output tube and consequently a somewhat higher B+ power supply potential is normally required to correct for this voltage drop. This provision of such an increase in the initial B potential demands considerable additional cost in the design of the television receiver low voltage power supply.

In some television circuit arrangements, it is 4bili moreover desirable to employ a somewhat higher value of the operating potential than normally made available by conventional economical low voltage power supplies. In this respect, power'recovery systems of the B boost type are of additional value in that the energy recovered from the deection circuit is utilized to establish a boost voltage above the available low voltage power supply of several hundred volts or more. Particularly in conventional forms of direct drive deflection systems, however, in which B boost power supply action is attained, the resulting boost `and voltage has in it an alternating current pulse component which is generally undesirable. Grdinary` lter arrangements for eliminating this undesirable pulse component due to kickback in the deflection system either unduly load the deflection yoke itself or result in an extremely `high terminal impedance for the boosted voltage.

It was with these considerations in mind that the low cost deflection system of the above referenced copending U..S. patent application, Ser. No. 90,612, Patent No. 2,555,831, was conceived. Now, however, modern day trends lean toward the provision of the above mentioned zoom control. Zoom control allows the deflection amplitude developed by the deflection circuit to be instantaneously jumped from one value to another. When the deflection amplitude increases over normaLthis makes the center of the television picture appear to be magnified.

. VThe present invention aims to provide 1a high efciency lowcost reaction scanning system of the direct drive B boost type whichA has a zoom type yamplitude control ofthe developed deiiection stimulus.

It is therefore 4a purpose of the present invention to provide an improved form of reaction scanning power recoverypdamping system for direct drive electromagnetic beam deflection systems which exhibits an eflicient B boost action 'coupled with an attendant high degree' of deflection linearity Yand instantaneous type amplitude zcontrol. 5

It is another object of the present invention .to provide a B boost reaction scanningsystem f for direct-coupled electromagnetic `deflection yokes which provide boosted terminal voltage having a ripple component substantially lower than prior art systems of a similar general type yet permitting the system to have a very versatile control of deiiection amplitude.

It is another purpose of the present invention to provide an improved form of zoom type de- `ection circuit for television systems wherein a portion of the cyclically damped reactiveenergy in the yoke circuit is applied for effectively boosting the available polarizing potential of the driving' vacuum tube. Y

Still Aanother object of the present invention resides `in the provision of a novel form of power recovery and amplitude control system particufA larly applicable to directly driven electromagnetic deflection coils in television systems wherein the deflection coils are included in the series with the anode-cathode circuit of the deflection sys- `tem driving vacuum tube.

In Yorder to realize the above, objects and features of the following example of a specific embodimentv of the present invention may be con sidered. For instance, the direct drive deflection system of the type shown in the above referenced Tourshou patent application 99,612, Patent No. 2,555,831 requiresa deflection yoke to be placed in'series with va rst capacitor between the anode vof-ftlriedeflection output Ytube and a vsource of +B power. 'Ihe system further provides that an inductance and capacitance combination may be `saine time causing its amplitude to vary over a relatively wide range.

The present invention has numerous other objectsand features. of advantage, some of which,

togetherwithv the foregoing will be set forth in the following description of specific apparatus embodying and utilizing the inventions novel method. It is therefore to be understood that the present invention is not limited in any way tothe apparatus shown in the specific embodiments as other advantageous applications in accord with the present invention, as set,forth -in the appended claims, will occur` to those skilled in the art after having benefited from the teachings of thev following description especially when considered in connection with the accompanying drawings in l which:

Figure 1 schematically illustrates one form of the present invention as applied to a television type cathode ray beam deflection system.

Figure 2 is a schematic representation of another form of the present invention as applied to a typical television receiver.

Figure 3 graphically illustrates certain waveforms peculiar to the operation oi the rpresent invention.

For purposes of clarity, full consideration will first be given to the general direct drive deflection system described in the above mentioned patentapplication by Simeon Tourshou, Ser. No. 90,612, filed April 30, 1949, now Patent No. 2,555,831. After understanding its rather complex operating principles, then special attention will be directed to those improvements on the Tourshou circuit which comprise the subject of the present invention. Therefore, let us turn to Figure 1, which illustrates a conventional form .of television deflection circuit. There is shown at I0 a source of sawtooth deflection signal having a waveform substantially as illustrated at I4. A synchronizing signal may be applied to the terminal I5 for synchronizing the developed sawtooth signal I4. The developed sawtooth signal is then applied tothe'control grid I8 of a cathode follower type amplifier stage employing discharge tube 20. The anode 22 of the discharge tube 20 receives a suitable positive bias through dropping resistor 24 connected with a source of positive potential 25, by-pass condenser 23 maintaining the anode 22 at substantially A. C. ground potential. VConnected between the cathode V3f! of the cathode follower amplifier and a source of nega-` tive biasing potential 32 is a cathode follower load resistor 34 whose upper end is directly coupled to the control grid 36 of the deflection output discharge tube 38. The resulting low impedance of the cathode follower circuit permits higher amplitude drive of the control grid 36 without encountering undesirable distortion due to grid current flow. A suitable cathode biasing M! is connected between the cathode 42 of discharge tube 38 and ground potential, by-pass capacitor 44 being provided to reduce degenera- .tion in the cathode circuit. A screen grid 45 is l'connected with a source of positive potential 48 in turn by-passed to the capacitor 52.

According to the previous arrangement described in the above mentioned U. S. patent application Ser; No.y 90,612, now Patent No. 2,555,- 831, in order to achieve B boost power recovery reaction scanning with the deection yoke 54, positioned for deflection of the beam in the cathode ray tube 5B, the upper terminal 58 of the yoke 54 is connected with the driver tube anode 50 Vthrough B boost capacitor 52, which in turn is connected with the primary 64 of the pulse step-up autotransformer 66. The lower terminal 68 of the deection winding is then connected with a source of positive potential 'l0 from which is supplied energy to the deflection circuit. A damping diode 12 is provided for damping the deection yoke 54 and is connected in shunt therewith through capacitor 14 as well as through *variable linearity control inductance 16 and capacitor 62.

The form of high voltage power supply for the accelerating anode 18 of the kinescope 56 is based upon the high voltage pulse step-up transformer 65 and is disclosed in more detail in the above noted Patent No. 2,555,827. As more fully described in the related specincation, the deection current for the yoke winding 54 must pass through the primary 64 of the autotransformer 56 and therefore induces in the secondary 88 high voltage positive going pulses corresponding in time to the retrace portion of the deflection cycle. These high voltage pulses are then rectified by the diode 82 to develop a high unidirectional potential across the storage capacitor 84. The voltage appearing thereacross is then applied through the iilter resistor 86 to the accelerating terminal 18 of the cathode ray tube 58. The auxiliary winding 88 of the autotransformer 66 supplies heater power for the lament 98 of the high voltage rectifier 82.

The operation of the general Tourshou deection system upon which the present invention is based may be best understood through reference to the curves of Figure 3. For purposes of simbe seen to operate as a reaction type of scanning circuit, that is, the desired sawtooth of current through the deflection yoke 54 is comprised of two sections, namely, a rst portion produced by anode current (ip) of the driver tube 38 (shown in curve 3a) and a second portion provided by current (id) representing magnetic energy stored in the deiiection yoke and damped by the damper tube 12, As is well known to those skilled in the art, in such a system the driver tube 38 is biased sufficiently beyond cut-01T such that only the upper portion of the sawtooth I4 causes conduction in the anode circuit. With normal 'circuit operating eiiciency, this conduction period T4 represents a little more than half of the linear grise time T1 of the current sawtooth having a period of T. In Figure 3a at the end of the time T1 which represents the positive peak of the driving sawtooth i 4, the discharge tube 38 is rendered non-conductive by the downward vertical portion oi' the sawtooth. However, the energy represented by the current in the yoke 54 at that time causes the yoke circuit and its associated stray capacitance to begin free oscillation. After a half cycle of free oscillation, the upper end 58 of the deiiectionyoke 54 then starts to go negacathode by means of` doing produces current in the direction of the arrow id at 92. The direction of now of this current ia as illustrated in Figure 3b is opposite to the current ip in Figure 3a so that two current flow curves id and ip in Figures 3a and 3b will tend to merge as in Figure 3c to form a substantially linear sawtooth rise time T1. Since this rise time represents a linear increase in current now through the yoke 54, during the time T1, it is evident that the voltage developed across the yoke terminals will be substantially equal to di Lai But, since during conduction of the damping diode l2, the cathode 'I3 thereof is held at positive B+ potential of terminal 78,` the capacitor v62 in combination with capacitor 14 and inductance 16 will charge up to substantially the value of di Ldt thereby making the loop voltage of the damped yoke circuit necessarily equal to zero. As indicated by the direction of current o'w id, the capacitors 62 and 'I4 will charge up in such a direction to increase the effective plate potential applied to the driver tube 38 at the time of its next conduction period commencing shortlybefore the end of T3.

Further considering the Tourshou direct drive system, it is seen then that the positive potential developed across the capacitors 82 and i4 will represent a portion of magnetic energy stored in the yoke 54 at the end of the linear rise time T4. As noted, the conduction of the damper diode l2 prevents the terminal 58 of the deflection yoke from going appreciably more negative with respect to ground than the positive B potential at terminal lil. The average B boost thereby represented by the stored energy on capacitors 62 and '14 may be illustrated by dashed line 94 in Figure 3d. Dashed line Sli is merely the A. C. axis of the yoke voltage Ey which, as stated, cannot go appreciably more negative than -l-B. Thus, the average potential boosty in the circuit will be presented by the volta-ge Eb dened byl dashed line 94 in Figure 3d.

According to the previous description of the Tourshou system, the sawtooth of current developed through the yoke 54 would be presumed to be substantially linear and except for the presence of the inductance 'i8 in Figure 1 would be substantially linear. However, as was shown in U. S. Patent 2,440,418, entitled Cathode Ray Beam Deflecting Circuit issued April 27, 1948, in

Ytelevision practice it is generally desirable t0 vachieve thiseimprovement in beam distribution 7 scanning vlinearity may be best discerned by curvesFigure V3g! and Figure 3h. lFigure 3g represents the voltage appearing across the capacitor .62- vdue to that `portion of the yoke sawtooth of current passing' therethrough while the voltage appearing across capacitor le, due to that portion of yoke current passing through it is shown by curve 3h. By properly relating the .values of capacitor B2'to capacitorflli in combination with the choice of inductance 16, the magnitudes of the two voltages in Figures 3g and 3h canbe controlled.y Since these voltages in fact appear in series 4withthe Vanode circuit of the vacuum tube 38 as well as the damper diode l2, they ywill contribute in determining the waveform of the current passing through the yoke. The resulting voltage therefore appearing across the yoke 54 will be somewhat as shown in Figure 3f which can be seen to agree with the desirably yoke current characteristics as set forth in Figure 3e.

In the Tourshou direct drive system, by varying the inductance l, the phase and magnitude of the ripple-voltage appearing across the capacitors 62 and 'lll ca n be changed relative to one another thereby permitting quite a versatile control over the scanning linearity produced by the circuit.

f The general direct drive deflection arrangement shown in a specic form in Figure 1, may be practiced in a variety of forms, one or" which forms i having other features of advantage is vshown in Figure 2. Here a typical television re- Iever arrangement is illustrated comprising a receiver section i90, which may include the wellknown television receiving components such as an RF amplifier, an oscillator, a converter, an IF amplifier, video demodulator, and video amplier. The output of the video amplifier is indicated for connection to the grid of a kinescope such as 5G which is also shown in Figure 1 and duplicated in Figure 2 for sake of descriptive simplicity. The television receiving arrangement also includes a sync separator |94, whose output is applied to synchronize a horizontal deilection signal generator IBB and vertical deflection circuit 108. The output of the vertical deflection circuit is available at terminals X-X indicated for connection to the vertical deflection yoke X-X at HG. The horizontal deilection signal generator m6 may be compared to the deection signal generator lil of Figure 1 taken in combination with the cathode follower amplifier 20, so that the output vacuum tube 38 may be properly driven with a sawtooth of voltage. Again for sake of simplicity, the circuit arrangement of Figure 1, as wellas corresponding indexes, have been duplicated Wherever possible in Figure 2. Examples of typical circuit arrangement applicable to the functions depicted by the various blocks'of Figure 2 are given in an article entitled Television Receivers by Antony Wright appearing in the March 1947 issue of RCA Review. Normal B-loperating potential for the various blocks is i1- lustrated as being provided at H0, the B+ power supply connections themselves being indicated by darker lines.

As hereinabove noted in television circuit design, it is oftentimes desirable to supply a particular circuit with a higher operating potential than nominally supplied by the B power supply unit for the remainder of the associated circuits. For example, in Figure 2 it may perhaps be desirable to supply the vertical deflection circuit |08 with-an `increased B+ voperating poten- 8 tial inorderto achieve suicient deflection swine in the vertical yoke winding X---XKl Of course, in vFigure 1, terminal H0 of storage capacitor 62 will evidence an increasedr positive potential due tothe power recovery B boost action hereinabove described. However, at terminal H0, which is at the upper end of the deiiection yoke winding 5d, there also appears a rather high positively going pulse during the retrace period as .evidenced by Figure 3d. In order to satisfactori- Y ly apply the potential at terminal l l0 to the vertical deilection circuit, it would then be necessary to accomplish substantial ltering of the voltage which calls for the use of an additional filter inductance and capacitance combination or a somewhat less expensive RC type of filter. A1- though considerably more economical, the RC filter would-have the disadvantage of expressing amuch higher terminal impedance to the vertical deflection circuit which in some instances would prohibit its use.

According to Figure 2, and stillconsidering the Tours/hou direct drive system, the basic B boost action of Figure l is preserved, but is rearranged so that the actual boosted B voltage appears at the lower end of the deflection yoke 54 and therefore does not include the higher potential positive-going ily-back or retrace pulse. This can be seen by noting that in Figure 2, the primary of the autotransformer 66 is directly connected to the terminal 58 of the deflection winding 5d while the counter parts of capacitance lli, inductance l', and storage capacitor 62 are respectively at ld', it and 2 in Figure 2. Nomina1 B power supply potential for the operation of the deflection circuit is applied at terminal H2 of the inductance 'i6 whereas the B boost Voltage appears at terminal |14 of storage capacitor E2. Since a parabolic voltage, such as shown in FiguresA 3g and 3h are respectively developed across capacitors 62 and '34', with the variable inductance 16, connected therebetween, the saine type of linearity control action will be obtained as in Figure l. Inasmuch as the voltage appearing at terminal Il li, although not containing the high amplitude y-back pulse of Figure k3 does contain a small amount of ripple voltage, it should be filtered to some extent such Vas bya relatively low impedance RC network comprising resistor H6 and capacitor H1. The

,voltage then appearing across capacitor H'l will .be substantially equal to `the boosted voltage EbY illustratedat Figure 3d. This may be applied directly to the vertical deflection circuit |98 as shown. v

In the operation of the basic Tourshou direct drive deflection system in Figures l and 2, on which the present invention is based, it has been described that the actual B boost power recovery action isachieved by cyclically capturing magnetic energy stored in the deflection yoke by means of the damping diode'Z and applying the same to the B boost capacitors 62 and 74. Although this forms one of the basic operating principles underlying the Tourshou arrangement, the most eiicient operation and satisfactory utilization of. the invention is made rpossible by a somewhat detailed consideration of various other factors involved in its operation which, due to their rather obscure nature and a present deside to impart a clear understanding of general circuit operation, have hereinabove been intentionally omitted.

Thus inthe 'Tourshou system and looking at Figure 1, and more particularly Figure 2, let there pacitance 39 (shown in dotted lines)u of the output tube 38, as well as the shuntcapacitances 55 and l, respectively representing the `well-known yoke balancing capacity and overall yokeshunt terminal capacitance. rThrough the series resonant circuit, iormed by the combined effects of capacitors 55 and 5?, the primary of the vhigh voltage pulse step-up transformert, the output capacitance 39 of the vacuum tube 38, and the .B boost capacitor S2 acting through the chassis ground and the B power supply l it, some ofthe energy stored in the pulse step-up transformer primary S4 will nd `transfer to -the,.lBj boost capacitors t2 andll during the retrace portion of the deflection cycle. This comes about by way of the fact that at the beginning of the retracemterval at which time, as hereinbeforevdescribed, vacuum tube 38 is rendered non-conductive, the magnetic energy stored in the primary 54 will cause the` series resonant circuit just described to commence ringing or oscillating'. lI he frequency of this ringing will be made a function-of the primary shunt capacitance 65 acting across the inductance t! as well as the remaining circuit stray capacitance actingdthrough ground. If now the frequency of the transformer primary resonant circuit is properly adjustedrelative to the resonant frequency of the series circuit formed by the yoke 54 taken in combination with its overall shunt capacitances 5t and 5l, the ringing of the high voltage transformer primary may be allowed to complete sufficient free oscillation to actually supplementV the terminal voltage of the yoke stray capacitance 57. This occurs at a time when the terminal voltage of the yoke 5d would otherwise be measurably lower. Of course, this action will increase the actual energy damped by the damper It and correspondingly, the B boost energy applied to the storage capacitors 62 and 'It'.

In accordance with the present invention a novel instantaneous width control is provided for the above described Tourshou direct drive deflection circuit. This is accomplished by conditionally switching in a sweep expanding circuit in shunt with the above described linearity inductance and B boost capacitor conguration of the Tourshou circuit.

For example, the sweep expanding circuit of the present invention is applied to the arrangement of Fig. 1, comprises the series combination of capacitor H6, inductance I8 and capacitor 2. A single throw, double pole switch ,or the equivalent is then provided having armatures |22 and |24 respectively cooperating with contacts |26 and |28. The opposite extremities of inductance ||8 are connected with the contacts |26 and |28.

Should now, according to the present invention, it be desired to expand the eiective sweep deiiection of the circuit shown, all that is necessary is to close the single throw, double pole switch. When this is done the inductance HB, is placed in shunt with the inductance 76 while the capacitors H6 and |20 are respectively placed in shunt with the capacitors 62 and 14. It is important to notice that 4by closing the single throw, double pole switch the values o1" capacitors 62, 14, as well as the inductance 'I6 are concomitantly altered. The eiective inductance in series with the deflection damping circuit will of course be less while the effective capacitor will be greater.

Similarly, in Fig. 2 the sweep expanding circuit of Fig. 1 has been shown as applied to the linearity inductance and .B boost capacitor conguration comprising capacitor M', inductance V'Iii' and capacitor 62. The double pole, single throw switch i3!) is connected in the same manner as the switch in Fig. 1. When the switch |30 is closed vthe inductance I8 in Fig. 2 is placed in shunt with the inductance 7S. At the same time capacitor H6 is placed in shunt with capacitor i4- and capacitor |20' is placed in shunt with the capacitor E2. This will increase the effective deflection amplitude through the deflection yoke 54.

-It is to be noted that in some instances'the connection of the sweep expanding circuit of the present invention as Yshown in Figs. 1 and 2 may produce some non-linearity at the view peaks of the deiiection sawtooth. However, this is of no importance since these peaks correspond to beam positions on the cathode ray tube falling outside the normal viewing area as of course must be ,the case if effective picture magnication is to be realized byl sweep expansion techniques.

Having thus described our invention what we claim is:

1. In an electromagnetic cathode ray deection system in combination, output terminals across which is developed a deflection wave form, an electromagnetic deflection yoke, a first capacitor connected in series with said deflection yoke to form a combination, connections placing said capacitor and yoke combination in shunt with said y outputl terminals, a first inductance and second capacitor connected `in series to form a combination, connections placing said inductance capacivtor series combinationin shunt ,with a portion of said yoke capacitor combination and embracing said first capacitor, a damping device connected in shunt with said yoke capacitor combination through at least a portion of said inductance, a third and fourth capacitor adapted for conditional shunt connection across said rst and second capacitors respectively, a second inductance adapted for conditional shunt connection with said rst inductance, and switching means for concomitantly establishing said third and fourth capacitors in respective shunt connection with said first and second capacitors, and said sec- .ond inductance in shunt with said rst inductor.

2. Apparatus according to claim 1 wherein said output terminals are established in the output anode cathode circuit of an electron discharge tube such that one output terminal is connected with said discharge anode and the other output terminal is connected to said discharge tube cathode and wherein said first capacitor is connected between said discharge tube anode output ter-` minal and said deection yoke.

3. Apparatus according to claim 1 wherein said output terminals are established in the output anode cathode circuit of an electron discharge tube such that one output terminal is connected with said discharge anode and the other output terminal is connected to said discharge tube cathode and wherein said rst capacitor is connected between said discharge tube cathode output terminal and said deflection yoke.

4. In an electromagnetic cathode ray beam deilection system employing a deection yoke, the combination of input terminals adapted to receive a deflection wave form suitable for application to the deflection yoke, iirst variable capacitive means connected in series with the deflection yoke to form a yoke capacitor combination, a second variable capacitor and variable inductance means connected in series t0 form an inassen# ductance capacitor combination,V connections vplacing said inductance capacitor combination in shunt with the portion of said capacitor yoke combination which embraces said iirst 'variable capacitive means, damping means connected betweenl said Variable inductance means and the terminal of the deiiection yoke not connected with said rst variable capacitive means, and means for concomitantly increasing the capacitive value of said variable -capacitive means at the. same time decreasing the inductance -value of said variable inductance means. Y

5. In an electromagnetic cathode ray beam dei' Flection system employing la deflection yoke, `the combination of input lterminals, ladapted to receve a deflection wave form suitable forvapplication to the deiiectionyoke, rst Variable capaci- Ytive means connected in ser-ies with the deflection Vyoke to form a yoke capacitor combination,A a second variable capacit/or and variable inductance means connected in series to form an inductance capacitor combination, connections placing said inductance capacitor combination in shunt with Y the portion of said inductance yoke combination which embraces said rst Variable capacitive'` means, damping means connected between said variable inductance means and the terminal of the deflection yoke not connected with said iirst Yvariable capacitive means,` and means for concomitantly varying said first 'and second variable capacitive means in a capacitive increasing direction while at the same time Varying said variable inductance means in an inductance decreasing direction.

6, Apparatus according to claim 5 wherein said input terminals are supplied with a deflection sig- Vnal by an electron discharge tube `ampliiier having at least an anode and vcathode and wherein said anode ris connected to one of said input terminals designated as the first input terminal, while an anode supply potential source is connected betweenv said discharge tube cathode and said other input terminal designated as 'the second input terminal.

'1. Apparatus according to claim-6 wherein said iirst variable capacitive means is connected between saidiirst input terminal and the deiiection yoke.

8. Apparatus according to claim 6 wherein said rst variable capacitive means -is connected-between said second input terminal and said deflection yoke.

9. Apparatus according to claim 6 wherein there is additional inductance means connected between one of said input terminals and-said yoke capacitor combination but embraced by the shunt connection of saidvvariable inductance capacitor combination.

SDVIEON I. TOURSI-IOU. ROBERT G. WOLCOTT.

Raritan-NCES CITED The following references are of record 'in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,470,197 lTorsch May 17, 1949 2,499,080 Webb r Feb. 28, 1950 

